1. Field of the Invention
This invention relates to signal prediction, and more particularly, to a long term prediction method and apparatus for polyphonic audio signal prediction in coding and network systems.
2. Description of the Related Art
(Note: This application references a number of different publications as indicated throughout the specification by one or more reference numbers within brackets, e.g., [x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.)
Virtually all audio signals consist of naturally occurring sounds that are periodic in nature. Efficient prediction of these periodic components is critical to numerous important applications such as audio compression, audio networking, audio delivery to mobile devices, and audio source separation. While the prediction of monophonic audio (which consists of a single periodic component) is a largely solved problem, where the solution employs a long-term prediction (LTP) filter, no truly efficient prediction technique is known for the overwhelmingly more important case of polyphonic audio signals that contain a mixture of multiple periodic components. Specifically, most audio content is polyphonic in nature, including virtually all music signals.
In addition, a wide range of applications such as multimedia streaming, online radio, and high-definition teleconferencing are enabled by transmission of audio over networks. However, a rapid increase in the “always-connected” user base has exacerbated the problem of unreliable channel conditions, prominently in the ubiquitous wireless and mobile communication channels, leading to intermittent loss of data. An effective frame loss concealment (FLC) technique plays an important role in gracefully handling this loss of data. Despite extensive industrial efforts, state-of-the-art FLC techniques do not offer efficient solutions for the important case of polyphonic audio signals, including virtually all music signals, where the signal comprises a mixture of multiple periodic components.
To better understand the problems of the prior art, some background information regarding prior art compression technology and networking (frame loss concealment) may be useful.